The present invention provides lower cost and/or safer pressure controllable coiled string operations that are preferable to the higher cost operations comprising, e.g., jointed pipe operations with hydraulic workover units and/or drilling rigs carrying out snubbing and stripping operations or well kill and open bore operations.
The present invention relates, generally, to methods and apparatus for piloting and traversing tool strings through deformed or restricted wellbore passageway walls or deformed and restricted wellbore passageway walls by, e.g., cleaning, cutting, bending or abrading the substantially differing diameters along a passageway's walls to remove the frictional forces preventing access or passage. The present invention can be usable with well intervention, abandonment, suspension and/or planned side-tracking operations where the proximally contiguous but erratic well bore axis and/or substantially differing wall circumference along a passageway as a consequence of, e.g., collapse, damage, scale build-up, hole fill, and/or completion tailpipe limitations, prevent or restrict conventional and prior art access to a lower end of a well bore. Conventional or prior art downhole devices can be piloted by the present invention to provide access and passage to said lower end of a wellbore.
The present methods and apparatus can be used to provide access to a lower end of a wellbore through an impasse using various conventional downhole devices selectively arranged to pilot or enlarge an existing frictional or restricted passageway that forms obstructive dissimilar contiguous well bore walls. Embodiments can pilot a tool string to displace debris within, and/or to deform, the proximally circular and/or deformed wellbore's walls. Embodiments may be used to deploy and orient various prior art downhole devices, relative to a proximal axis or proximally contiguous wall, by using the expandable and collapsible members of the present invention, which can be engaged about a plurality of shaft segments that can be usable to pilot tool string embodiments through said impasse or restriction using, e.g., sliding, bending or vibration to circumvent the restraining friction or restrictions to, in use, traverse around said impasse. Embodiments can also include the use of various explosive, hydraulic, electric and/or rotary forces to cut or wedge dissimilar contiguous passageway walls.
Tool string embodiments of the present invention can use the interoperability between coiled string conveyable tools and shafts to pilot the tool string to provide access and to forcibly deform substantially differing circumferences along a wellbore's axis or a contiguous but changing axis. The tool string can be controllably used to deliver substantial hydraulic and explosive forces to, e.g., compress, crush, press, impact, cut, perforate, shear, enlarge or otherwise displace intervening frictional debris or restrictions in or within a wall of a wellbore to provide passage from one passageway to a substantially differing diameter of contiguous passageway, and/or an axially differing subterranean passageway, to provide access or passage to the lower end of a well bore.
The present invention can be used with any type of deployment string, including a coiled string, providing significant benefit over prior art and being applicable to a significantly larger population of wells. Typically, coiled string applications have lower costs with lower well control risks due to the greater pressure control provided by a grease head or stuffing box seal around coiled strings during deployment through the existing above surface well barrier pressure containment envelope, which may be left in place.
The methods and apparatus of the present invention can provide for well intervention, where none has been possible previously, to provide significant benefits. The references cited below, typical of prior art, generally pertain to wireline and coiled string deployment using the limited force of conventional tools that are unable to orient explosive devices axially, because said prior art may be, e.g., propelled out of the well or otherwise become damaged or stuck within the wellbore if operated with the same hydraulic and/or explosive forces that can be usable with the present invention. The present invention can provide the additional benefit of friction reducing methods and apparatus, which can be conventionally usable with coiled tubing and drill strings, but unavailable to wireline.
Existing devices, for example, U.S. Pat. No. 2,618,345, teach wireline conveyable, expandable, axial, pivotal spring slips that are usable with a conical packer engagement to a wall of a well bore; however, such devices, as described in U.S. Pat. No. 2,618,345, could not be fashioned to be movable or to achieve the expanded-diameter-to-collapsed-diameter ratio necessary for passage through, e.g., a collapsed conduit bore's walls. Similarly, U.S. Pat. No. 2,942,666 teaches an expandable membrane with axial pivotal slips for securing a bridge plug or packer within a well, wherein the expanded-diameter-to-collapsed-diameter is greater, and whereby the tool may be deployed through significantly smaller diameters, then enlarged and engaged to the well bore wall; however, like U.S. Pat. No. 2,618,345, U.S. Pat. No. 2,942,666 is intended to be fixed to a bore and not piloted and traversed through obstructive dissimilar contiguous wellbore walls. U.S. Pat. No. 2,761,384 teaches the use of explosives to cut a conduit downhole, but, as is common to such applications, cutting of the conduit occurs transverse to the conduit's axis. Accordingly, if the visual similarity of deployment or fixing of such downhole devices through or to a wellbore wall, or explosively cutting conduits downhole, was obvious, disclosure of U.S. Pat. No. 2,618,345, U.S. Pat. No. 2,761,384 and U.S. Pat. No. 2,942,666 filed in 1948, 1951 and 1956 would have rendered the majority of the remaining cited references obvious.
The methods and apparatus of the present invention provide access or passage through a dissimilar contiguous passageway, and there has been an unresolved need in the oil and gas industry for this technology.
References, such as U.S. Pat. No. 3,187,813, relate to wireline dumping of cement upon, for example, a restriction or bridge plug, as provided by the teachings of U.S. Pat. No. 3,282,347, U.S. Pat. No. 3,481,402, U.S. Pat. No. 3,891,034, U.S. Pat. No. 3,872,925, U.S. Pat. No. 4,349,071, U.S. Pat. No. 4,554,973, U.S. Pat. No. 4,671,356, U.S. Pat. No. 4,696,343, U.S. Pat. No. 5,228,519, U.S. Pat. No. 6,050,336, U.S. Pat. No. 6,341,654, U.S. Pat. No. 6,454,001, U.S. Pat. No. 7,617,880, U.S. Pat. No. 7,681,651, US 2007/0107913 and US 2008/0230235, which recite various baskets, bridge plugs and/or bladders and expandable or axial pivotal wall securing engagements that are visually similar to U.S. Pat. No. 2,618,345 and U.S. Pat. No. 2,942,666, but do not teach the passage of a downhole device past an obstructive restriction. Such prior art may also include the deformable members taught in U.S. Pat. No. 6,896,049, which can be used in a downhole device, and which is silent to the potential deformity of well conduits and piloting of such devices into, e.g., a damaged or debris filled wellbore.
The majority of the existing practices presume a circular well bore without significant restriction to deployment of a downhole device; for example, U.S. Pat. No. 4,696,343 and U.S. Pat. No. 6,454,001 are usable for passage of an axial pivotal collapsed and expandable wireline operable umbrella or basket, deployable through a casing into a substantially different diameter open or uncased open strata hole for engagement with the wall of a well, but are silent to deployment through, for example, a collapsed casing.
Prior art teaches various setting tools, such as U.S. Pat. No. 5,392,856 and U.S. Pat. No. 7,172,028, for baskets, umbrellas and bailers that are usable in, e.g., a wellbore plug back operation, wherein the setting tools may include various triggers, timers, springs, battery packs and/or releasable differential pressure vessels usable for the necessary energy to actuate downhole devices.
However, the prior art is, generally, silent to practicable cost effective means of deploying or urging a downhole device's deployment through, for example, the debris of a collapsed casing section. Despite teaching debris management, U.S. Pat. No. 8,109,331 is silent to the debris of well component failures, like casing or tubing collapse and, generally, cannot be oriented axially downward to either cut or expand a failed well conduit. Similarly, U.S. Pat. No. 5,154,230 teaches the repair of a liner, and the explosive shape charges of U.S. Pat. No. 8,166,882 may be used to cut, for example, a failed and/or collapsed well conduit traverse to a well conduit axis, while U.S. Pat. No. 6,076,601, U.S. Pat. No. 6,805,056 and U.S. Pat. No. 7,591,318 provide a method and apparatus usable for explosively cutting, U.S. Pat. No. 7,591,318 discloses the cutting of a downhole plug and pushing it downhole, and wherein U.S. Pat. No. 7,591,318's numerous cited references teach various means of deforming a downhole well bore; however, the prior art does not teach a practicable means of piloting and orienting “axial” cutting tools downward to sculpt through and/or expand, e.g., the collapsed portion of a deformed liner, and whereby the downward orientation of such prior art would result in launching said prior art upward within the well bore, in a manner similar to a bullet being shot from the barrel of a rifle.
GB2486591, of the present inventor, teaches stator rotation within rotary milling tools using a hydrodynamic fluid bearing arrangement, while US 2011/0168447 teaches a means for passage of a casing through the proximally circular or deformed circumference of a well bore filled with, for example, cuttings from boring, whereby turbine blades are used about the circumference of the downhole device to move debris with a reamer shoe for placement of casing; however, the application is silent regarding cable or wireline compatible deployment of a downhole apparatus, wherein the use of fluid to operate such a turbine from a cable engagement is far from obvious within a obstructive dissimilar contiguous passageway, where circumferences and diameters may significantly vary.
US 2008/0217019, U.S. Pat. No. 7,878,247, U.S. Pat. No. 7,905,291B2, U.S. Pat. No. 4,350,204, US 2010/0032154 and US 2011/0240058 teach various coiled string compatible methods and apparatus for access or passage through a well bore filled with, e.g., cuttings or scale in vertical and horizontal wells, albeit said access and passage comprises the removal of the debris through circulation as a tool string is deployed into a wellbore, wherein the obstruction is always below or in front of the tools string, and whereby said prior art is silent to the interoperability between tools in the deployment string that is necessary to pilot a tool string and traverse through intermediate debris and/or damaged walls, to the lower end of a wellbore, without the removal of said debris and/or damaged walls through the act of milling and well bore circulation.
Various conventional practices may be arranged and deployed using the present invention's methods and/or piloted by the present invention's apparatus. In practice, because the embodiments of the present invention have not been used or practiced in the industry, it is not known, to the oil and gas industry, how smaller and lower cost conventional practices or prior art might be practicably deployed for repeated access and to provide passage to a well's lower end by selective arrangement, piloting and orientation of a tool string relative to substantially differing circumferences along an erratic axis of a contiguous passageway's walls, which can be formed by deformation or damage along and/or debris within or along the dissimilar passageway walls, which is taught herein.
The present invention solves various problems existing in the oil and gas industry, which include the problems described by FIGS. 8 to 11, 14 to 17, and 21, wherein well conduits of significant wall thickness, metal grade and hardness have been collapsed and/or sheared by moving subterranean strata above a carbonate reservoir being driven by a water flood, and whereby the conventional use of milling operations has been unsatisfactory for various reasons, including inadvertent side-tracking of wells, which would result in a complete loss of access to a producing reservoir. Generally, a lack of cementation behind various casing strings, which resulted from difficulties during well construction and were compounded by movable strata formations, could result in leak paths and associated reservoir pressure control issues during conventional milling and/or after abandonment of the well's lower end.
The present invention provides solutions to the industry's problems, as shown FIGS. 8 to 11, 14 to 17, and 21, and the methods and apparatus of the present invention can be adapted for use with conventional downhole devices in addition to the downhole devices of the present inventor.
The methods and apparatus of the present invention can be adapted to be compatible with the present inventor's methods and apparatus of GB2484166A to provide the safe abandonment of damaged wellbores and/or bores with oval shaped casing circumferences that can reduce the effectiveness of, e.g., piston packers, for the crushing of well components to form a geologic sealable space.
Typically, subterranean wells target and exploit subterranean deposits of hydrocarbons, geothermal heat sinks, salt layers or other subterranean features that, generally, have been formed by natural stratigraphic traps and subterranean movements of strata within the earth's crust, which have trapped and formed the desired deposit.
While said strata movements may have trapped the deposits over a geologic time frame, the using or exploiting of a subterranean deposit can change the subterranean pressures and/or the original in place rock stresses formed before exploitation of the deposit. Pressures within strata pore spaces and/or connecting fault planes about a well bore may be increased by injection (e.g. from a water flood) or depleted (e.g. by production) and, thus, can promote or attract fluid pressure and/or strata movements, dependent upon the ability to transmit pressure, that can cause subterranean strata to shift over the life of a well. For example, if an impermeable layer of strata separates a higher pressure porous and/or permeable layer from a lower pressure porous and/or permeable layer, the higher pressure may act upon the impermeable strata and form a very large stratigraphic piston with substantial associated forces comprising the pressure differential multiplied by the area affected, which will typically be measured in square miles or kilometers. When a reservoir pressure is depleted and pressures above the reservoir cannot equalize with the depleted reservoir strata, movement, typically referred to as subsidence, may occur. The injection of water using, e.g., a water flood may tend to equalize pressures or provide insufficient pressure support and/or, exacerbate pressure differentials to lubricate strata faults and cause increased strata movement, which may not necessarily be vertical subsidence, but also lateral shearing.
Protection from various strata layers and the fluid pressure within said strata are, generally, provided by well conduit linings hung from a surface wellhead, commonly referred to as casings, while protective well linings hung from a previous casing are, generally, referred to as liners.
Well construction comprises boring through the subterranean strata, placing protective conduit casings or liners, and cementing the conduits in place prior to using the conduit casings and/or liners, for further boring and/or as a secondary pressure barrier, about a production or storage tubing and associated subterranean completion equipment. Production tubing, packers, control lines, subsurface safety valves and other completion equipment are installed within the casing and/or liner conduits to provide a primary completion pressure barrier within said secondary casing and/or liner barriers, which can prevent the unplanned escape of fluids from a well into the subterranean strata or surface environments.
The intermediate annulus between the completion and casing and/or liner conduits is, generally, a void space used to monitor the status of the primary barrier. This annulus may be used during well construction when a heavy fluid is present within the annulus and/or blowout preventers are placed on the wellhead to provide well control to, for example, place a gravel pack. Once the completion is installed, the blowout preventers must be replaced by the well's valve tree, generally referred to as a Xmas tree. The intermediate annuli, generally, become fluid filled voids used for monitoring the primary and secondary barriers, but they can be used to, for example, provide gas lift to the completion production conduit in wells that are generally incapable of producing significant quantities on their own without stimulation. Other power fluids, such as injected water, may also be circulated through the annulus to operate a jet or a hydraulic pump; or, alternatively, an electrical submersible pump, rod pump or pump jack can be used for wells requiring stimulation to produce in meaningful quantities.
It should be understood that the Xmas tree, wellhead and casings are generally the first and last barriers between subterranean fluids and the surface environment, wherein said casings and completion components deep within a well, generally, have access to annuli passageways connected directly to the surface; hence, the failure of well casings, kilometers below the earth's surface, may represent a serious problem to the surface environment.
Movements or shifting of the subterranean strata from, for example, subsidence of the heavy overburden, hydration and activation of shale, or flowing of mobile salts, can adversely affect and damage casings, liners and completion components through the application of collapse, burst, tensile and/or compressive forces.
The conventional remedy for damaged subterraneanly installed casings, liners and/or completion equipment is their removal through what are generally termed “fishing” operations, since damaged equipment may be difficult to catch and remove, wherein the ability and associated probability of engaging or “catching” and “removing” the “fish” or damaged equipment is uncertain. “Fishing” items that have fallen downhole can be undertaken using various jointed or coiled strings, for example wireline or coiled tubing, whereas heavy duty hydraulic workover units and/or drilling rigs are conventionally used for fishing of heavy components, such as casings, liners and completion equipment. Additionally, when damaged subterranean equipment cannot be “fished” from the well, it may be ground or milled into small pieces with a rotary drilling rig or hydraulic workover unit to facilitate its removal by using the circulating system to lift said small pieces.
Failures of well components above the lower end of a well are particularly problematic because intermediate well damage may prevent access to the lower end of the well and/or expose lower end well pressures to upper end well components, which are unsuited for such pressures or the forces associated with such abnormal pressure.
Unfortunately, the failure of downhole components and their associated primary and secondary barriers may expose various other well components to forces and pressures that may cause further failure and, ultimately, the unintended release of subterranean fluids to the surface, or other permeable subterranean formations. For example, casing barriers are conventionally designed to withstand the pressures at the lower end depth of casing placement, typically referred to as the “casing shoe.” When a secondary deep casing barrier fails and deeper subterranean pressures are placed within the surrounding annulus pressure void, the shallower and lower pressure resistant tertiary casing barriers may have insufficient pressure bearing capacity for said deeper pressure communication and may also fail, and so on and so forth, until the final barrier fails and an unplanned release of fluid from a well occurs.
Furthermore, fishing operations for heavy workover units and drilling rigs are particularly difficult and dangerous within a pressurized environment resulting from such failures, where fishing equipment must be snubbed into a well through the blowout preventer while damaged equipment is stripped out of the well through blowout preventers. The blowout preventers must be opened and closed around the varying diameter of tools joints and pipe bodies for each joint snubbed in or stripped out, wherein the design of the blowout preventers requires a circular circumference and, hence, cannot not seal against the deformed conduit circumferences.
Within explosive hydrocarbon environments, where repeated wear and tear from snubbing and stripping operations may weaken the sealing capacity of blowout preventers, unintended hydrocarbon leakage may occur. Snubbing and stripping operations are considered extremely risky operations by industry, wherein snubbing and stripping practitioners are considered to be the highest risk tolerance workers within the industry, purportedly out of necessity rather than choice.
Since the failure of various well components, like casings, liners and the surrounding sealing cement can provide leak paths, which are not necessarily accessible to kill fluids during a well kill operation or stoppable by the wellhead or blowout preventers, and the pressures exerted during a kill operation may aggravate said leak paths, the failure of downhole conduits poses a serious risk. Additionally, since snubbing and stripping blowout preventers are engaged to the existing wellhead and/or Xmas tree, they may not provide the necessary blow out protection in instances where well casings have failed beneath the wellhead.
Accordingly, a need exists for methods and apparatus usable with coiled string operations that can re-establish access or passage to the lower end of a well through the debris and/or damaged walls of an intermediate well conduit failure to provide access for isolating production from damaged well equipment sections, and using, e.g., the apparatus and method of GB1111482.4, prior to repairing a damaged section or abandoning the damaged section of a well. Coiled string operations can be more easily and safely carried out through pressure controlled equipment, without adversely affecting or further damaging subterranean well equipment, with the pressures exerted by, e.g., a heavy well kill fluid. The conventional need for expensive and potentially more dangerous fishing and milling operations, using a hydraulic workover unit or drilling rig, may not be necessary.
Additionally, a need exists for apparatus and methods that can use explosives axially within a well and can absorb axial fluid pressure shocks or fluid hammer effects upon well equipment when using focused explosives. A further need exists for focusing an axial fluid shock or fluid hammer effect, in a selectively oriented direction, to aid in re-establishing access to the lower end of the well through intermediately damaged well bore walls.
Well component failure can also occur as a result of operational wear from using a well, particularly with regard to thermal and operation cycling when producing and shutting in production. Since subterranean strata generally gets hotter with depth, due to the heat radiated from the earth's molten mantle core, produced fluids can carry that heat from the strata and cause components of a well to expand with production and contract when production is stopped as shallower, lower temperature strata, less affected by the molten mantle core, cool the various portions of the completion. The cycling of production and production shut-in causes associated expansion, contraction, pressure ballooning and/or movement of well components that may repeatedly stress and/or erode said components to the point of failure.
Conventionally, movement of the production conduit strings, which are placed within cemented-in-place liners and casings, is facilitated by applying tension during the installation of said production conduit strings to reduce physical movement and associated wear, at the expense of placing additional stresses upon components, which may be aggravated by thermal expansion and contraction.
Various conventional provisions are available for allowing movement of components, such as expansion joints to absorb movement, which may use seal stack mandrels at the lower end of the production conduit string, within a polished bore receptacle (PBR) that can be engaged to a liner top packer or production packer secured to said casings, wherein an expansion joint can reduce the stresses associated with thermal expansion and contraction, but increases physical movement and associated wear and tear on moving completion components during cycling of production and production shut-in.
Accordingly, the well completion may comprise a simple tubing string within a casing with a valve tree at its upper end and a production packer at its lower end, with tensioned tubing between, or it may have, e.g., subsurface safety valves and associated control lines, sliding side doors for opening and closing a passageway between the production conduit and intermediate annulus, PBR's, seal stack mandrels, jet pumps, hydraulic pumps, rods, side pocket mandrels for associated gas lift valves, and/or various other completion components, each of which may fail with operational stresses, wherein movement of the completion and/or movement within the surrounding strata can damage the well bore's walls, thereby making the piloting of a tool string through failed components conventionally difficult.
Over the life of a well, the well components and well production casing or liners and conduits may be adversely affected by: chemically corrosive fluids; solids and fluids erosion; subterranean temperatures and/or pressures causing flexure, expansion and/or contraction; vibration, wear or frictional deformation from interaction between various downhole well completion components or from drill strings, wireline, coiled tubing or other tools operating on or adjacent to well components; as well as plastic deformation caused by strata shearing, thrusting or subsidence movement from, e.g., movement of mobile subterranean salt formation or overlaying pressurized overburden strata forces on produced and depleted formations, which can cause slumping or shifting and/or movements of strata due to hydration or lubrication of shale, clays or other strata within the overburden due to water ingress from natural or induced faults, fractures, water floods and/or faulty well cement isolation from water bearing formations, water floods or natural water drives.
Various adverse conditions can render a well inoperable from a pressure and fluid integrity perspective and/or prevent deployment of downhole apparatuses necessary to, for example, repair the effected portions of a well, suspend portions of a well for later repair, abandon portions of a well that cannot be repaired, and/or side-track portions of a well to provide further production.
A need exists for accessing various portions of a well through differing types of debris and damage using less intrusive coiled string operations through an existing pressure control envelope to provide access through a damaged portion, which can be for other coiled strings used to repair or abandon a section or isolate pressures from a damaged portion to provide safer operations than, e.g., jointed pipe stripping and snubbing operations.
As casing and/or liners are, generally, cemented within the strata, even minor movements of the strata, around conduit casings and liners, may cause said conduits to become oval in shape while more severe movement can collapse or shear said conduits. Rupture of various components within a well may also expose other components to subterranean pressures for which they were not designed. For example, if a secondary conduit barrier, such as the production casing, is leaking from wear caused by movement of the tubing and the tubing then ruptures, pressure could be placed on the intermediate and surface casings, which could cause them to burst and release fluids to the environment.
Attempting to fish or mill damaged components that are not axially aligned with the centre of a well bore can lead to inadvertent side-tracking of a well, wherein access to the original and damaged well bore may be lost and which can potentially cause a serious pressure control situation, as pressures continue to leak through the damaged portion, which may no longer be accessible as a result of the incidental side-tracking.
A need exists for methods and apparatus usable to traverse axially obstructive discontinuous portions through an intermediate well bore failure without side-tracking the well during repairs and/or accessing a proximally axial contiguous passageway, so as to access and isolate pressures from said failure at their source.
Temperature cycling from, for example, repeatedly starting and stopping production can adversely affect a completion, casing and/or liner components, while significant temperature increases in a confined annulus can cause significant pressure and may plastically collapse or burst well components. Component failures from, for example, a tubing leak at the upper end of a tubing string may not burst the production casing, but may increase the pressure within the annulus sufficiently enough to collapse the tubing at the lower end of the well, when combined with the hydrostatic pressure of the fluid within the annulus.
A need exists for apparatus and methods usable for less intrusive coiled string interventions, which are capable of, for example, providing a passageway through a tubing collapse and then repairing said tubing collapse with, for example, an expandable metal patch, to allow, e.g., bull-head killing of a pressurized reservoir through the repaired production tubing.
Alternatively, the build-up of scale within tubing over the life of a well can be significant and may choke off production significantly. A need exists for tools capable of engaging and cleaning scale debris from a production casing to provide an access passageway through the tubing to, for example, set plugs within nipples, clean downhole valves, side-pocket mandrels and/or inject or use a wireline dump bailer to place chemicals to further clear scale from various downhole well components.
Accordingly, over the productive life of a well, many factors may adversely affect the components of the well and prematurely end the useful life of a portion of the well, the entire well or its economic life, whereby the suspension, abandonment and/or side-tracking of all or a portion of the well is necessary but impractical with conventional means.
A need exists for a more cost effective means of providing access to a well portion clogged by debris or that has been damaged.
Passage of both fluids and tooling within a well may be adversely affected by, e.g., debris within a bore from sand production from a reservoir, or shale production from a flow cut conduit or scale from production, or the passage may be adversely affected by deformation of conduits by movement of the surrounding strata, differential pressures across conduits and/or wear and tear from operation of the well.
A need exists for apparatus and methods usable for coiled string compatible passage of downhole apparatuses and fluids through the proximally circular and deformed circumferences of a well bore.
The need for fluid or tool communication is particularly acute during the suspension, side-tracking and/or abandonment of a well bore, because subterranean pressures within a bore must be sealed from depleted formations and the surface environment. The prevention of fluid communication and/or loss of fluids, from a deposit into other depleted and/or permeable formations or strata factures and/or the protection of a reservoir deposit or production stream from, e.g., water ingress, is important to our economy.
A need exists to access passageways below an intermediate well bore failure without removing surface well barrier pressure control envelopes to reduce the risk of unplanned releases of well fluids that endanger the surface environment, endanger sensitive strata formations, e.g., ground water horizons, and waste presently unrecoverable subterranean deposits that may be recoverable later by, e.g., using technology that has not yet been invented.
Various aspects of the present invention address these needs.